Hej!
[tex](2a+3b)(b-3)+(3b+1)(2b-5a)=\\\\=2ab-6a+3b^2-9b+(6b^2-15ab+2b-5a)=\\\\=2ab-6a+3b^2-9b+6b^2-15ab+2b-5a=\\\\=\underline{9b^2-13ab-11a-7b}[/tex]
Pozdrawiam! - Julka
